J. Agronomy and Crop Science 159, 82—89 (1987)© 1987 Paul Parey Scientific Publishers, Berlin and HamburgISSN 0931-2250

Dedicated to Professor Dr. G. Geisler on his 60th birthday

Contribution from Institute of Crop Science and Plant Breeding,University of Kiel

Yielding Ability of Pure Stands and Equal Proportion Blends ofRapeseed {Brassica napus L.) with Double-low Quality

J. L£ON and W. DIEPENBROCK

Authors' address: Priv.-Doz. Dr. W. DIEPENBROCK and Dr. J. LtON, Institute of Crop Science and PlantBreeding, University of Kiel, Olshausenstrafie 40—60, D-2300 Kiel.

With 7 tables

Received April 9, 1987; accepted April 23, 1987

Abstract

Yielding ability of intraspecific mixtures is an important issue not only for homozygous and homogeneouscrops but also for heterozygous and/or heterogeneous ones. The goal of the present study was to examine theperformance of mixtures and synthetics from double-low (low in erucic acid and glucosinolates) rapeseed{Brassica napus L.) as compared to pure stands. The material consisted of seven lines and from 1982/83 to 1984/85 lines, all possible biblends and syn,'s (1983/84 and 1984/85 exclusively) were grown in a completelyrandomized block design. An analysis of variance was conducted and general mixing effects (g.m.e.) andspecific mixing effects (s.m.e.) were calculated for components of biblends. A few pure-standing hnes yieldedhigher than some mixtures. Nevertheless, the overall mean of mixtures was not exceeded by any pure st^d.For selection purposes, the higher variance of 'among lines' in comparison with 'among blends' would notresult in higher yields because of the generally higher yielding ability of blends. Additionally, mixtures weremarked by higher yield stability as compared to pure-standing lines. On the average of two years of testingyields of syn,'s amounted higher than yields of mixtures. Differences between 'g.m.e.' of lines were provedand moreover, the variance component of 's.m.e.' was on a lower level than that of 'g.m.e.'. Consequently, inorder to find the best mixture it seemed not necessary to analyse a complete diallel rather than to applyfactorial or incomplete factorial concepts.

Key words: Brassica napus L.; yielding ability; mixtures; double-low quality.

Introduction

Investigations on intraspecific mixtures haveoften been done with homozygous andhomogeneous cultivars of self-pollinatedcrops. These blends were usually higher ingrain yield as related to the mean of the com-ponents in pure stands (PFAHLER and LINSKENS

1979, ScHUTZ and BRIM 1971). There alsoexisted cases that a mixture had outyielded thehighest-yielding component (BAKER and BRIGGS

1984, REICH and ATKINS 1970, SHORTER and

FREY 1979, NiTZSCHE and HESSELBACH 1983,1984).

Mixtures of heterozygous and homogeneousmaize {Zea mays L.) hybrids produced yieldson an equal level as compared to the mid-component mean (EBERHART et al. 1964,HoEKSTRA et al. 1985, KANNENBERG andHUNTER 1972, THOMPSON 1977). But, there arealso results from JURADO-TOVAR and COMPTON

(1974), KANNENBERG (1974) and HOHN (1978)that mixtures yielded both above and belowthe means of the pure stands.

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Yielding Ability of Pure Stands and Equal Proportion Blends of Rapeseed 83

Like hybrids cultivars of vegetative prop-agated crops are highly heterozygous andhomogeneous. As an example for this categoryDoNEY et al. (1965) observed an enhancedtuber production for mixtures of potato clones(Solanum tuherosum L.).

Much less information is available on cross-pollinated or partial cross-pollinated crops.Blends of allogameous crops were reported tooutyield their component mean, e.g. PFAHLER

(1965) proved two-variety-blends of rye {Sec-ale cereale L.) to yield equally to the bestcomponent.

Considering stability of yields blends ofhomogeneous genotypes (heterozygous as wellas homozygous) were more stable thanexpected from the mean of genotypes (com-pare QuALSET and GRANGER 1970, REICH andATKINS 1970, SCHUTZ and BRIM 1971, FEASTER

and TuRCOTTE 1973, PFAHLER and LINSKENS

1979, ScHNELL and BECKER 1986, LEON 1987).Therefore, blends might be superior to theircomponents not only with regard to yield butalso to yield stability.

For rapeseed {Brassica napus L.) SCHUSTER

(1982) emphasized that synthetic varieties out-yielded their components by 10 %. It washypothesized that the surplus was caused bymixing effects, genotypic combining abilityand also by the outcrossing rate of the partialallogameous rapeseed.

The objective of the present study was toevaluate the peformance of mixtures andsynthetics from double-low (low in erucic acidand glucosinolates) material of rapeseed ascompared to pure stands. As from n compo-nents n (n-l)/2 biblends can be produced, moreinformation about general and specific mixingeffects of the components is needed to selectreliably the highest yielding blends. So, specialregard was paid to general and specific mixingeffects within the tested material.

related as less as possible the complete material origi-nated from three different breeders. All possibleequal proportion biblends were produced by seed-mixing taking account of thousand seed weights.Additionally, for each pair of lines syni was estab-lished by multiplication of the mixed parents in thefield under natural conditions.

The material was grown at the experimental sta-tion of the Institute of Crop Science and PlantBreeding near Kiel, Schleswig-Holstein, on a sandy-loam soil during three years from 1982/83 to 1984/85.During the first year lines and blends were tested andsimultaneously syn,'s were produced. During thegrowing seasons 1983/84 and 1984/85 the completematerial was investigated lines, blends and syn,'sincluded. The experiment was arranged in a com-pletely randomized block design with 6 replications.The plots were 2.50 m wide and 4.00 m long. Plantdensity amounted to 80 plants/m" in autumn. Fer-tilizer was applied to a rate of 200 kg N/ha in springand 120 kg P^Os/ha and 240 kg K^O/ha in autumn(presowing). Crop protection was carried outaccording to the local standard. Seed-yield per plotwas adjusted to 9 % moisture content and thenconverted to dt/ha.

Within each year the correlation between plotyields and the mean of two left and right neighbour-ing plots was calculated. In the case of significantcorrelations the nearest neighbour analysis (WlLKlN-SON et al. 1983) was conducted. The loss of degreesof freedom due to the nearest neighbour analysis wasconsidered for the analysis of variance. 'Years','lines' and 'blends' were regarded as 'random'. Thedesign of mixing corresponded to the diallel designoften used in plant breeding research and, Griffing'sconcept of general and specific combining ability wasapplied to estimate general mixing effects (g.m.e.)and specific mixing effects (s.m.e.) for the compo-nents of blends (compare FEDERER et al. 1982).Because of significant differences between lines andblends only blends were involved in the statisticalanalysis. Both 'g.m.e.' and 's.m.e.' were regarded as'random'.

For the statistical tests of significance the commonsigns are used: +, '•' and '•'• = significance at 0.10,0.05 and 0.01 level of error-probability.

Material and Methods

The material used for this experiment consisted ofseven rapeseed {Brassica napus L.) lines with 'dou-ble-low'-quality as follows: Librador, WRG 19(DSV Lippstadt-Bremen GmbH, Postfach 1407, D-4780 Lippstadt), Jade, Saphir, Chr. 2648/80, Br.1657/79 (Norddeutsche Pflanzenzucht Hans-GeorgLembke KG, Hohenlieth, D-2331 Holtsee),RAW 242 (Lochow-Petkus GmbH, Postfach 1311,D-3103 Bergen 1). In order to ensure that lines are

Results

The combined analysis of variance calculatedfor seed yield (dt/ha) is given in Table 1. Meansquares of 'years' and 'entries^'years' werehighly significant. Subdivision of 'entries' dis-played differences between 'lines' and 'blends'on the 10 % level of probability. These differ-ences were not influenced by 'years'. Interac-tions 'among lines '•' years' and 'among blends

84 LtON and DiEPENBROCK

Table 1. Combined analysis of variance for seed-yield (dt/ha) of lines and blends grown during 1982/83 to1984/85

Source of variation

yearsblock within yearsentries

lines vs. blendsamong linesamong blends

entries '• years(lines vs. blends) '•' years(among lines) "•• years(among blends) " years

error

D.F. M.S. Variance components

2141716205421240311

1772.23==-==-17.9745.46

1429.52-h56.0837.4035.64= =34.5848.55==- -31.83= =16.89

11.64

0.61

0.470.353.5105.942.80

'=- years' were proved to be highly significant.The variance component of the interaction'among lines'"'"years' amounted more than two-fold as high as the corresponding value of'among blends ==years' and, furthermore, thevariance component of 'among lines' rankedconsiderably higher than that of 'amongblends'. The standard deviation of variancecomponents amounted 1.33 and 3.47 for theinteractions 'among blends ''"'' years' and'among lines ''•' years', respectively.

The analysis of variance for yields (dt/ha)gathered in two years of testing is presented inTable 2 with special consideration of synthe-

tics (syn's). An overall effect of years could beneglected but, mean squares for 'entries "'years' were highly significant. Subdivision ofinteractions concerned with yearly effectsrevealed significant mean squares for '(blendsvs. syni) '' years', 'among lines "' years' and'among syni ''•' years'. A general differencebetween blends and syn/s occurred at the10 % level of probability whereas meansquares within syni's differed insignificantly.

Means of seed yield (dt/ha) from lines,blends and syni's are grouped for each of 3years separately (Tab.3). Blends yielded about6 % higher than lines and syni's surpassed

Table 2. Combined analysis of variance for seed-yield (dt/ha) of lines, blends and syn,'s grown during 1983/84to 1984/85

Source of variation D.F. M.S.

yearsblocks within yearsentries

lines vs. blends, syn,'sblends vs. synj'samong linesamong blendsamong syn/s

entries ''' years(lines vs. blends, synrs) ''' years(blends vs. syn/s) '' years(among lines) "' years(among blends) •' years(among syn/s) "' years

error

11048

116

202048

116

2020

363

0.66

44.73103.95135.86+42.6545.07+37.51

0.03

226.16=---

23.52+32.12=^16.87

Yielding Ability of

Table 3. Seed-yield

Pure Stands and Equal Proportion

means (dt/ha) for lines, blends and

year82/83 83/84

Blends

syn,'s

of Rapeseed

84/85mean

all years

85

mean(83/84 + 84/85)

linesblendssyn,'smeanmean(lines and blends only)

22.8125.28

24.05

LSD.05

27.95 31.5730.34 31.6532.27 31.9130.19 31.7129.14 31.61

lines vs. blendslines vs. syn,blends vs.

27.44

29.09

28.27

1.53

29.76

30.99

32.09

30.95

30.38

1.72

1.19

Table 4. Analysis of variance of general (g.m.e.) and specific mixing effects (s.m.e.)

Source of variation D.F. M.S. Variance components

g.m.e.s.m.e.g.m.e. "• yearss.m.e. '•' yearserror

61412

28311

95.40+48.7438.2946.71==-==

16.89

0.690.1305.59

Table 5. Seed-yield means (dt/ha) of lines (main diagonal), blends (lower left) and values for specific mixingeffects (upper right) and for general mixing effects (g.m.e.)

LibradorWRG 19JadeSaphirChr.2648/80Br. 1657/79RAW242

mean ofbiblends

28.4330.2528.1028.3430.0629.7928.62

Librador

27.2430.8328.0327.2028.8329.6320.06

WRG19

1.4926.8327.5229.9231.7032.4429.07

Jade

-0.23-1.6527.6617.7528.6825.8630.77

Saphir

-1.180.63

-0.4727.5627.6130.0727.43

Chr.2648/80

-0.411.55

-0.40-1.5928.3032.9630.58

Br.1657/79

0.572.42

-3.091.003.03

27.9827.79

RAW242

-2.46-0.362.41

-0.991.24

-1.4226.51

g.m.e.

-0.651.17

-0.98-0.740.980.71

-0.46

Table 6. Seed-yield means (dt/ha) of lines (main diagonal), blends (lower left) and syn,'s (upper rieht) erownduring 1983/84 and 1984/85

LibradorWRG19JadeSaphirChr.2648/80Br. 1657/79RAW242

mean ofbiblends

30.6532.4929.9529.6831.7231.8930.53

Librador

29.8833.8229.1527.9832.2932.5228.21

WRG 19

34.9930.7330.8831.5133.2034.6630.90

Jade

32.0528.9129.7929.2529.7128.1432.56

Saphir

33.1431.5433.5929.4427.7431.1430.45

Chr.2648/80

31.2429.7431.2836.0030.5335.5931.79

Br.1657/79

35.6832.0429.3032.8931.3829.7729.33

RAW242

32.1932.0431.6232.0631.9530.2828.13

mean ofsyn,

33.2131.5431.1233.2031.9331.9231.69

86

Table83 to

7. Combined1984/85

Source of variation

analysis of variance for thousand-seed-weight

D.F.

(g) of lines

M.S.

and

L£ON and DiEPENBROCK

blends grown during 1982/

Variance components

yearsblocks within yearsentries

lines vs. blendsamong linesamong blends

entries ==' years(lines vs. blends) ==' years(among lines) ==' years(among blends) == years

error

214

27

1

6

2054

2

12

40

311

43.1546==-*

0.1516

0.4404==-

0.4521

0.8684+

0.3273

0.2362==-==-

0.1651

0.3052=-^

0.2191--'=-

0.0982

0.2876

0.0128

0.0373

0.0068

0.02600

0.0390

0.0228

even blends. On no account, the interaction'(blends vs. syn,) ==' years' had caused anychanges of rank order in single years. Hence,within each year of testing blends were moreproductive than lines and, moreover, syn/srevealed throughout higher yields than didblends.

Blends were composed according to the dial-lel design. Consequently, the analysis of var-iance could be subdivided to general mixingeffects (g.m.e.) and to specific mixing effects(s.m.e.) (Tab. 4). The interaction 's.m.e. ""years' was highly significant and differencesbetween g.m.e.-effects could be verified on the10 % level of probability. It was also observedthat lines per se and the general mixing effectsvaried independently (r = 0.22).

Table 5 contains both seed-yields (dt/ha) onthe average of 3 years of blends or lines andvalues for g.m.e. and s.m.e. Means for allblends of each line involved generally exceededthe pure stand of the respective line. Remark-ably, the highest-yielding pure standing line ishardly adequate to an average blend. Compo-nents with the highest general mixing effects(WRG 19, Chr. 2648/80, Br. 1657/79) contrib-uted to the best blends (WRG 19 + Chr. 2648/80, WRG 19 + Br. \e'b7/79, Chr. 2648/80 +Br. 1657/79). Blends produced by one of themost effective pure-standing lines G * )ranged on a comparatively low level because ofthe minor general mixing effect of this line.

Means of lines, blends and syni's are pre-sented in Table 6. All of them were testedduring 1983/84 and 1984/85. As to each line therespective mean of blends outyielded the pure-

standing line. With the exception of WRG 19this is also true for the mean of syni's ascompared to the mean of blends. A correlationbetween blends and respective syni's could notbe verified.

The combined analysis of variance forthousand-seed-weight becomes apparent fromTable 7. The values for lines were basicly notdifferent from those for blends. Among linesdifferences obviously occurred while thiscould not be proved for blends. Correspondin-gly, the component of variance for 'amonglines' amounted higher than for 'amongblends'. Interactions between 'entries '=" years'were highly significant with regard to both'among lines '"'•' years' and 'among blends *years'. The variance component of the interac-tion 'among lines "• years' was higher than thatconcerned with blends.

Discussion

Seed yields of blends surpassed the perform-ance of pure standing lines. In the presentinvestigation blends had derived from lineswhich were also tested in pure stands. Genefrequencies were equal for means of bothblends and pure stands and therefore, thesemeans were principally comparable. Differ-ences in seed yield could be attributed to thegenetic structure of lines and blends whichwere homogeneous and heterogeneous,respectively. HUHN and SCHUSTER (1975) andLeoN (1987) found positive mixing effectsamounting to similar quantities and L£ON(1987) emphasized that these effects could be

Yielding Ability of Pure Stands and Equal Proportion Blends of Rapeseed 87

verified with homozygous as well as heterozy-gous stands of rapeseed.

The material of the own experiment con-sisted of lines with 'double-low' quality. Thelowered glucosinolate content was primarilyselected from the polish cultivar 'Bronowski'representing the exclusive source of this trait inmodem varieties. Therefore, especially thefirst lines with 'double-low' quality are nearlyrelated. Furthermore, inheritance ofglucosinolates with maternal predeterminationas described for the partial allogame rapeseedplant implies a considerable high number ofselfings to produce seed with low and stableglucosinolate content. So, lines with 'double-low' quality are expected to be ratherhomogeneous. The present results demon-strated significant positive mixing effectswhich were not influenced by 'years' althoughfor other crops no differences occurredbetween blends and pure stands (e.g. SIMMONDS

1962, TRENBATH 1974, HoEKSTRAet al. 1985).

In detail, a few pure-standing lines yieldedhigher than some mixtures. Nevertheless, theoverall mean of mixtures was not exceeded byany pure stand. For selection purposes, thehigher variance of 'among lines' as comparedto 'among blends' would not result in higheryields because of the generally higher yieldingability of blends.

Differences between lines and blends werenot affected by 'years'. Although the differ-ence observed in 1984/85 was rather small therank order did not change throughout.According to SPRAGUE and FEDERER (1951) thevariance of the 'entries "=• environment'-interac-tion could serve as a measure to estimate yieldstability. The higher the variance of interac-tions amounted the more decreased the accu-racy for the prediction of the respective effects.The difference between the variance compo-nents of the interaction 'among lines "" years'and that of the interaction 'among blends '""years' was twofold as high as the standarddeviation of the variance component of theinteraction 'among blends ==- years'. Conse-quently, mixtures were generally marked byhigher yield stability as compared to pure-standing lines. This tendency is consistent withresults from LfiON (1987) elucidating highyield-stability of blends composed of rapeseedlines free from erucic acid ('single-low' quality)

and, there was further evidence that mixturesof homogeneous stands of other crops exhi-bited higher yield stability, too (QUALSET andGRANGER 1970 and PFAHLER and LINSKENS 1979

for oats, REICH and ATKINS 1970 and KOFOID etal. 1978 for Sorghum hicolor L., SCHUTZ andBRIM 1971 and WALKER and FEHR 1978 for soy-

bean and FEASTER and TURCOTTE 1973 forcotton).

Production and testing of all possible mix-tures from the seven Hnes allowed to calculate'general mixing effects (g.m.e.)' and 'specificmixing effects (s.m.e.)'. This approach isrelated to the diallel concept often applied inplant breeding research (GRIFFING 1956). Asmarked differences occurred between lines inpure stands and blends only blends were takeninto consideration. Differences between'g.m.e.' of lines were clearly shown and thevariance component of 's.m.e.' was on a ratherlow level as compared to that of 'g.m.e.' (ratio< 's.m.c./o g.m.e. = 0.188). Consequently, inorder to determine the best mixing partner itseemed not necessary to analyse a completediallel rather than to apply factorial or incom-plete factorial concepts (compare MELCHINGER

1984). In that model a certain proportion ofmixing partners would represent the steps of afactor and the remainders would stand forsteps of another factor. Because of the signifi-cant interaction 's.m.e. ==- year' replications ofsuch field trials should be conducted for sev-eral years and locations. But, further investiga-tions are needed to analyse whether more loca-tions would reduce the required number ofyears of testing.

Prediction of 'g.m.e.' could not be deducedfrom yields of pure stands because the corre-sponding coefficient of correlation (r = +0.22)was rather low.

The average yield of syni's amounted higherthan that of mixtures. This result obviouslycontradicted the finding of LEON (1987) that nosignificant differences occurred betweenbalanced sets of blends and the adequate syni'swith a defined degree of heterozygosity. How-ever, according to SCHUSTER and FRIEDT(1985)

yield performance of synthetic varieties of thepartial allogame rapeseed plant is basicly deter-mined by: 1. yield of component per se, 2.general and specific combining ability, 3. out-crossing rate, 4. mixing effects of components.

LtON and DiEPENBROCK

5. mixing effects between outcrossed andselfed progenies and 6. degree of inbreedingdepression of components.

Hence, the difference between blends andsyni's might also be ruled by these factors.Moreover, in contrast to the experiments ofLION (1987) the present data were based onnatural outcrossed populations possibly re-vealing a higher degree of heterozygosity.

The difference between blends and syn/swas significantly affected by years. Neverthe-less, no changes of the rank order of meanswere observed. Like blends, syni's showedcomparatively weak interactions with years.So, syni's generally were characterized byhigher yield-stability than pure standing lines.

As thousand seed weights (TSW) of blendsand pure stands were not significantly differ-ent, this yield component could be disregardedas a source of the above mentioned effects onyields. As a consequence, yield differenceswere entailed by the multiplication rate ofplants (seeds per plant). This could be animportant issue to forecast the yield of synthe-tic varieties.

With regard to TSW, interactions 'amonglines ''' years' and 'among blends '•* years'showed the same pattern as observed for yield.Again, the variance components of interactions'among lines '=" years' were higher than 'amongblends =" years'. Therefore, considering TSWstability of blends was strengthened as com-pared to lines.

Zusammenfassung

Ertragsfahigkeit von Reinbestanden und an-teilsgleichen Mischungen von Raps {Brassicanapus L.) mit Doppel-Null-Qualitat

Die Ertragsfahigkeit intraspezifischer Mi-schungen ist nicht nur fiir homozygote undhomogene, sondern auch fiir heterozygoteund/oder heterogene Kulturpflanzen von Be-deutung. Die Leistungen von Mischungen undSynthetics aus Rapslinien {Brassica napus L.)mit Doppel-Null-Qualitat (niedrige Gehaltean Erukasaure und Glukosinolaten) wurden imVergleich zu Reinbestanden untersucht. In denJahren 1982/83 bis 1984/85 wurden Reinbestan-de, alle moglichen Zweikomponentenmi-schungen und die entsprechenden Synthetics(nur 1983/84 und 1984/85) von sieben Linlen in

einer vollstandig randomisierten Blockanlagegepriift. Die Daten wurden varianzanalytischverrechnet und aufierdem sind allgemeine Mi-schungseffekte (g.m.e.) und spezifische Mi-schungseffekte (s.m.e.) der einzelnen Mi-schungskomponenten ermittelt worden. DieErtrage der besten Reinbestande lagen hoherals die einiger Mischungen; das Gesamtmittelder Mischungen wurde jedoch von keinemReinbestand iibertroffen. Hinsichtlich einerSelektion kann darauf verwiesen werden, dafidie hohere Varianz von ,innerhalb Linien' imVergleich zu ,innerhalb Mischungen' nicht fiirErtragssteigerungen genutzt werden kann,weil Mischungen durchschnittlich hohere Er-tragsleistungen aufwiesen als Reinbestande.Dariiber hinaus waren Mischungen durch einevergleichsweise hohe Ertragsstabilltat gekenn-zeichnet. Im Durchschnitt zweier Ver-suchsjahre iibertrafen die Syni-Ertrage die Er-trage von Mischungen. Zwischen den Linienwurden Unterschiede in allgemeinen Mi-schungseffekten nachgewiesen und ferner lagdie Varianzkomponente fiir spezifische Mi-schungseffekte auf einem niedrigeren Niveauals diejenige fiir allgemeine Mischungseffekte.Folglich ware die Analyse eines komplettenDiallels nicht notwendig, um die besten Mi-schungen aufzufinden, wozu faktorielle oderunvollstandig faktorielle Ansatze geniigenwiirden. '

Acknowledgements

The authors thank Prof. Dr. M. HUHN for criticalreading of the manuscript and Mrs. A. BRENNECKE

for ver> skilled technical assistance.

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